The present invention is directed to an electrostatic chuck for holding and positioning semiconductor substrates for processing of the substrate.
In semiconductor fabrication processes, electrostatic chucks are used to hold substrates for processing of the substrates. Generally, an electrostatic chuck comprises an insulator covering an electrode. Typically, the insulator and electrode are supported by a support adapted to be secured in a process chamber. An electrical connector electrically connects the electrode to a voltage supply source in the process chamber. When the electrode is electrically biased with respect to the substrate held on the chuck, opposing electrostatic charge accumulates in the electrode and substrate resulting in attractive electrostatic forces that hold the substrate to the chuck. Electrostatic chucks are generally described in, for example U.S. patent application Ser. Nos. 08/278,787 by Cameron, et al.; 08/276,735 by Shamouilian, et al.; and 08/189,562, by Shamouilian, et al. --all of which are incorporated herein by reference.
Conventional electrostatic chucks can also have coolant grooves for holding coolant for cooling the substrate held on the chuck, for example, coolant grooves extending through the insulator as described in U.S. patent application No. 08/276,735 to Shamouilian, et al. When a substrate is held on the chuck, the substrate covers and seals the coolant grooves so that the coolant held in the grooves does not leak out. Cooling of the substrate reduces overheating of the substrate to provide higher yields of integrated circuit chips from the substrate.
Conventional chucks can fail or have limited lifetimes in erosive process environments. For example, when the insulator of the chuck comprises a polymeric dielectric material, such as a polyimide, the polymeric insulator can be eroded by the erosive process environment, limiting the useful lifetime of the chuck. Erosion of polymeric insulators can be particularly severe in oxygen or halogen containing gases and plasmas, which are used for a variety of tasks, such as for example, etching of substrates and cleaning of process chambers. While a large portion of the polymeric insulator is typically covered by the substrate held on the chuck and thereby protected from the erosive environment, the periphery of the insulator is exposed to, and can be eroded by the erosive gaseous environment. The exposed polymeric insulator can erode in a few hours (typically 2 to 3 hours of exposure to a oxygen plasma environment), and erosion through a single point of the insulator can expose the electrode causing short-circuiting and failure of the chuck. Failure of the chuck during processing of the substrate can damage the substrate and reduce yields of the valuable integrated circuit chips processed on the substrate. Also, the polymeric byproducts formed by the erosion of the polymer dielectric often deposit on the chuck and walls of the process chamber to form hard polymeric deposits which are difficult to clean.
Thus, it is desirable to have an electrostatic chuck which demonstrates improved erosion resistance and reduced failure rates in erosive process environments. It is also desirable for the chuck to provide uniform cooling of the substrate held on the chuck to provide increased integrated circuit yields, particularly from the perimeter of the substrate.